ABSTRACT
Although it was postulated that APUD cells originated from the primitive neural crest, whether all APUD cells actually stem from this crest is uncertain. Although studies using quail and chick embryos cast doubt on the claim that APUD cells of the Gl tract originate from neural ectoderm, endocrine cells of the Gl tract and pancreas do possess an enzyme specific to neural cells (neuronal-specific enolase, NSE), which supports the hypothesis of a common neural origin. It is clear that neuroendocrine cells of the gut are remarkably similar to cells within the hypothalamic-pituitary axis. Gut endocrine cells may also be “neuroendocrinologically” programmed, even though their origin is not clearly understood, thereby giving validity to the concept of the gut acting as a “visceral brain.”
